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The Science of Microwave Popcorn: A Matter of Understanding Physical Changes

Retrieved from the Akron Global Polymer Academy at http://agpa.uakron.edu/p16/professional-development.php

Grades: 5-8
Author: Tony Gosmer

Abstract

Module Description:

This unique module of science and technology will give teachers the opportunity to explore the mysteries of microwave popcorn and the technologies that make it possible. In this process they will venture through a series of events in the investigation of the microwave popcorn bag. They will make inferences and hypothesis based on observations and prior knowledge. The participants will have a better understanding of scientific investigations in the areas of science and technology.

Objectives

Participants will explain how technology influences our daily lives.

Participants will explain how decisions about the use of products can result in desirable and undesirable consequences.

Participants will keep clear and accurate records while recording and interpreting data.

The following NSES indicators will be addressed in the engagement activities of this module:

Identify a physical change (popcorn).

Properly use appropriate tools and instruments (scale, thermometer) .

Materials

Procedures

The first two activities included in this module are designed to get the participants excited and engaged for the day's lesson. The first activity will demonstrate a simple physical science model that will parallel the physics inside the popcorn kernel. The second engagement activity will demonstrate how a physical change takes place inside the popcorn bag. Both activities can be used as either engagement activities or extension activities. Then, following the two engagement activities the lesson will move toward the Microwave Popcorn lesson.

Engagement: So what makes the popcorn pop?

Engagement activity #1


Engage a discussion as to the physics taking place inside the popcorn kernel.

Now place the canister with the water in it on a napkin with the open end of the canister facing up.

Assessment: Discuss and record observations in journal. How do you think this activity relates to popcorn? What changes are taking place inside the microwave popcorn package?

Exploration: You will need one triple bar scale for each team and one package of unpopped popcorn and explore the physics inside a popcorn bag.

Assessment: Discuss and record any changes in the popcorn or popcorn package.

Microwave popcorn lesson procedures:

Explanation: Review the teacher notes of the lesson for basic information involving polymeric technologies in the construction of microwave popcorn packages prior to your presentation. Discuss examples of how technology influences our daily lives (popcorn popping changed when the microwave oven got popular) and that sometimes technologies have undesirable consequences (How many times have you opened the popcorn bag and found lots of duds?). Have each participant think of ways that technology influences our lives an informal assessment and to demonstrate knowledge of the new material. For further information on polymers and popcorn see the credit/ references section of this module. See also Explanation of Science section below.

Elaboration: The microwave popcorn lesson provides us with a unique opportunity that encourages the participants to plan lessons that utilize inquiry investigations and the use of technology for learning. The participants will be able to elaborate thoughts and opinions through reflective writing. Give participants time to plan an inquiry-based lesson to deliver to their students - see lesson plan template.

Overall Assessment: Monitor participants throughout the session as outlined in the lesson for students.

Engage conversations throughout the lesson allowing for a question and "What do you think?" session.

Have participant's share journal reflections, thoughts and opinions. "How could we improve this lesson?"

Rationale

This module will give opportunities for various teaching methods; one such method is inquiry-based learning. This module will guide the participants through a series of simple activities that will allow for inquiry-based learning in the classroom where both the teacher and students have a positive experience. The engagement activities will provide simple opportunities to attempt inquiry learning, which can be accomplished at varied levels of skills and background knowledge.

Science Standards

National Content Standards A: Science as Inquiry; Content Standard B: Physical Science; Content Standard E: Science and Technology

The following indicators based on NSES content will be addressed through a series of engagement activities (see engagement section in procedures, see also extension activities)

Professional Development Standards

Best Teaching Practices

Time Frame

2 hours (+/- 20 minutes)

Preparation

Organize room to accommodate groups of no more than 2-3 participants.

Have room arranged to accommodate the expected number of participants. I would suggest having no more than 2-3 participants in each group as this will cut down on unnecessary chit-chat and annoying conversations that do not pertain to the module. Provide your name and contact information. Kindly ask all participants to place their cell phones on vibrate or place in off position, as this is another annoying disturbance that so often occurs during professional development sessions.

Do not place more than one microwave in any given electrical outlet. Contact the building supervisor for recommendations. Have paper towels and/or handy wipes available after handling popcorn.

Safety

Be conscious of extreme heat after removing popcorn from microwave (optional gloves). Make goggles or eye protection an option for the participants. If possible place all recyclable items in recycling bins.

Assessment

Monitor participants throughout the session as outlined in the lesson for students.

Engage conversations throughout the lesson allowing for a question and "What do you think?" session.

Have participant's share journal reflections, thoughts and opinions. "How could we improve this lesson?"

Explanation of Science

The film canister in engagement activity #1 represents the popcorn kernel's pericarp. When the Alka-Seltzer is dropped into the water, carbon dioxide gas forms. The enclosed canister allows the gas pressure to increase causing the lid to "pop", whereas the popcorn kernel's pericarp acts similar to the film canister. The heat forms steam inside the kernel, the pressure builds and the kernel "pops". The kernel contains a tiny amount of water, which undergoes a physical change from the heat (liquid to gas) as does the starch granules change into gelatinized globules (physical change).

The microwave popcorn bags vary in construction. One has a paper outer layer with a PET (same polymer that is found in the two-liter bottle) inner layer. The PET layer prevents the fat and oils to be absorbed by the paper outer layer. Paper is very inexpensive. There is a low melting adhesive for the ends so that when the popping cycle is almost complete, the seal melts in the steam, and opens the ends for gases to escape. The special layer for reradiating energy is located under the paper layer and inside the inner layer of a polymer film. This layer is called the susceptor and it is a metallized PET film. Aluminum is sprayed onto the film in a vacuum chamber to prepare this metallized film. All producers of these packages now use a susceptor in one geometry or another. They do not have to cover the entire package. The susceptor is placed on the bottom of the microwave oven with the corn resting on top. Other packages might use OPP (oriented polypropylene) for an overwrap which costs less than PET. The package is still evolving since manufacturers are striving to minimize unpopped kernels.

Popcorn contains mostly the translucent endosperm as opposed to the opaque endosperm. This endosperm is penetrated by the high pressure steam while the popcorn is heating. The starch granules change into gelatinized globules and then expand into thin fusible bubbles as the pericarp is burst by the pressure of the water vapor. The pericarp is the protective layer on the outside of the kernel. It breaks at about a pressure of 9 atmospheres. (ChemMatters October, 1984)

Handouts

None available for this module.

Extensions

Place a thermometer inside the popcorn bag immediately following removal from bag (be sure it is a thermometer suitable for extreme heat). Try this with various brands and flavors.

Determine the mass of a popped package of popcorn 1 day after popping (you would want to determine the mass after popping to compare).

Go to http://www.jollytime.com/kids_corner/ for more information and activities.

Lesson Implementation Template

Download Lesson Implementation Template: Word Document or PDF File

Equity

Take into consideration the diverse learning styles teacher as well as students have. Consider that you may have technical/confluent learners as well as precise/sequential learners of a variety of backgrounds. All of which interpret and process differently.

Resources

None available for this module.

References

The original Microwave Popcorn lesson was written by Mary Harris, Missouri Polymer Ambassador, Copyright 1998.

For more information on popcorn or polymers see these interesting websites:

http://www.foodqualitynews.com/news/ng.asp?id=59421


http://howthingswork.virginia.edu/ (search 'popcorn')

www.howstuffworks.com (search, 'microwave popcorn')

www.chemistry.org (popcorn)


http://maize.agron.iastate.edu/popcorn.html (why does popcorn pop?)

http://www.nationalgeographic.com/resources/ngo/education/plastics/ (polymers)





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